Chad is the fifth largest country in Africa and ranks second among Sahelian countries after Sudan. Chad’s land surface presents a dramatic variety of geographic contrasts. The vast northern third is located in the Sahara Desert and is sparsely populated, home to just 1 percent of Chad’s population. The whole central swath is in the Sahel, with average annual rainfall ranging from 150 to 600 mm. Both N’Djamena, the capital, and Lake Chad are found in this region. Lake Chad is fed by the country’s two main rivers, the Chari and the Logone. It is the largest body of water in the Sahel and a major center of economic activity for the region. However, due to erratic variations in the region’s climate and overexploitation of the rivers that feed it, this shallow lake (1.5 m deep on average) has shrunk to a small fraction of its 1960 size. Chad’s population lives mainly in the southern part of the country, in the more humid Sudanian climate zone, where average annual rainfall ranges between 600 and 1,300 mm. Southern Chad has the largest, relatively intact expanses of wooded savannas and woodlands of any of the Sahelian countries. Discovery of artifacts and fossils in northern Chad— especially the 7-million-year-old Toumaï skull from a hominid that is regarded as one of the oldest species in the human lineage — attests to the archaeological and historical richness of the country. Traditionally, Chad’s economy has been based on farming and livestock, but in the last decade the economy has changed dramatically from the oil boom. Besides oil, there are also significant deposits of gold, marble, and sodium carbonate.